Stitch width tracker for sewing machine

Abstract

A sewing machine has a vertical needle bar pivotable about a point thereon adjacent the upper end and moveable up and down. A sewing needle is detachably secured to the lower end of the bar and has an eye adjacent its lower end. The machine has an adjustable stitch width and, during its operation at a preset width, satisfies the requirement that the eye must be continuously properly positioned with respect to the machine hook at all times. The eye is vertically aligned with the hook point when the eye is in proximity of the hook, so as to insure reliable stitch formation at any selected stitch width. An arrangement for maintaining such proper positioning employs a first stop secured to the bar at a first location thereon intermediate its ends. A second stop is secured to the bar at a second and lower position intermediate its ends. A member is slidable along and is disposed on the bar in the space between the two stops. A spring is disposed on the bar between the first stop and the member. The member when moved upward to engage the spring causing the spring to exert a force on the first stop which moves the bar upwardly. The amount of upward movement of the bar is monotonically related to the amount of upward movement of the member. A device responsive to the movement of the hook engages the member to move the member upward in such manner as to maintain said proper positioning. The device includes a mechanism for pivoting the needle bar as required for zig zag operation and a stationary element disposed between the second stop and the member.

What is claimed is: 
     
       1. A sewing machine having a vertical needle bar pivotable about a point thereon adjacent an upper end thereof and moveable up and down, a sewing needle detachably secured at one end to a lower end of the bar, and having an eye adjacent the other end, and a hook having a point, the machine having an adjustable stitch width, an arrangement for vertically aligning the eye properly with respect to the hook at all times during an operation of the machine at a present width, so that the eye is vertically aligned with the hook point when the eye is in proximity of the hook at all times, said arrangement comprising: a first stop secured to said bar at a first location thereon intermediate the ends of the bar;   a second stop secured to the bar at a second and lower position intermediate the ends of the bar;   a member slidable along the bar and disposed on the bar in a space between the two stops;   a spring disposed on the bar between the first stop and the member, the member being moved upward to engage the spring so that the spring exerts a force on the first stop which moves the bar upwardly, the amount of upward movement of the bar being equally related to the amount of upward movement of the member; and   means responsive to the movement of the hook and engaging the member to move the member upward in such manner as to maintain said proper vertical alignment of needle eye and hook point, said means including a mechanism for pivoting the needle bar as required for a zig zag operation and a stationary element disposed between the second stop and the member.   
     
     
       2. The arrangement of claim 1 wherein said element includes a contoured slide plate which extends between the second stop and the member. 
     
     
       3. The arrangement of claim 2 wherein said plate has a slot through which the bar extends. 
     
     
       4. The arrangement of claim 3 wherein adjacent surfaces of the second stop and said member have roller means engaged by the plate.